H2O2 scavenging
H2O2-scavenging activity of the olive oils (IM < 2, 2012/2013 crop season) was measured using the procedure reported by Bahorun et al. (1996). To a solution of 3 × 10−3% H2O2 (100 μl), 0.1 M NaCl (100 μl) and 0.1 M phosphate buffer (pH 7.4, 700 μl) was added a methanolic solution of the olive oil (4.0 mg/ml, 100 μl), or pure MeOH (100 μl) instead of the sample, for the control. The corresponding mixture was incubated in the darkness at 37 °C for 20 min. Then, a solution containing phenol red (0.2 mg/ml) and horseradish peroxidase (0.1 mg/ml) in 0.1 M phosphate buffer (pH 7.4, 1.0 ml) was added. The corresponding solution was kept at 37 °C during 15 min. Then, 1 M NaOH (100 μl) was added, and the mixture was kept at room temperature for 10 min; after that, the absorbance was read at 610 nm against a blank. All the measurements were carried out in triplicate. The results are expressed as percentages of reduction of H2O2:
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AH2O2 refers to the control solution with MeOH instead of the sample, and Asample refers to the absorbance of the oil-containing solutions.